1. Field of the Invention
The present invention relates to a ranking document retrieval apparatus for giving priority to and presenting a retrieval result obtained by making retrievals in response to a retrieval request described in a natural language or a question consisting of inputted word strings, in descending order of document similarity.
2. Description of the Related Art
Conventionally, a ranking document retrieval apparatus gives priority to documents in descending order of similarity in response to a retrieval request inputted by a user and presents the retrieval result.
A ranking document retrieval technology is disclosed in, for example, “Managing Gigabytes, Compressing and Indexing Documents and Images, pp. 141-148.
Generally, a document similarity factor can be obtained by multiplying an importance degree in a document to be retrieved of a requested retrieval word (idf) by an importance degree in a respective document (tf).
However, usually, neither the importance degree of a word in a retrieval result nor a similarity retrieval method is disclosed to a user. Therefore, the operation is difficult for a user to understand.
Thus, if a document unexpectedly appears in a higher rank in response to a retrieval request, a user must estimate the movement of a ranking document retrieval apparatus and make retrievals by replacing a word or regenerating a question sentence (retrieval request), which is a problem.